I. Field of the Invention
The present invention relates to a circuit for protection against negative overvoltages across the power supply of an integrated circuit comprising a power device with related control circuit.
II. Prior Art and Other Considerations.
It is well known that power devices, together with the related control circuits, are used for driving loads of various types. If it is an inductive load, as in the case of a power device used in motor car applications, the cut-offs of the power device determine positive overvoltages across the power device itself which are normally absorbed by means of appropriate limiting devices such as zener diodes. It can, however, occur that such positive overvoltages across the power device combine with negative overvoltages across the source of the power supply, say, a motor vehicle's battery. In such cases, if the power device and the related control circuit are accomplished in the form of an integrated circuit, the parasite transistor formed between the collector of the power device and the power supply source can burn out.
The object of the present invention is to endow the integrated circuit with an adequate protection against the drawbacks due to such negative overvoltages.